1. Field of the Invention
The present invention relates to a semiconductor device having a circuit comprising a thin film transistor (hereinafter referred to as TFT). For example, the present invention relates to an electro-optical device, typically a liquid crystal display device, and an electronic device with an electro-optical device installed as a component.
Note that through this specification, a semiconductor device indicates general devices that can function by using semiconductor characteristics, and that electro-optical devices, semiconductor circuits, and electronic devices are all categorized as semiconductor devices.
2. Description of the Related Art
Techniques for using semiconductor thin films (with a thickness on the order of several nm to several hundreds of nm) formed on a substrate having an insulating surface to structure a thin film transistor (TFT) have been in the spotlight in recent years. Thin film transistors are widely applied to electronic devices such as ICs and electro-optical devices, and the rapid development thereof as switching elements for image display devices is desired.
For example, the application of TFTs is being attempted in every electric circuit in a liquid crystal display device, such as pixel matrix circuits that control each of the pixels, arranged in a matrix shape, driver circuits that control the pixel matrix circuits, and in addition, logic circuits (such as processor circuits and memory circuits) which process external data signals; in all electric circuits.
Conducting materials such as Al, Ta, and Ti are conventionally used as wiring materials for the above TFT, and among them aluminum that have low resistivity is often used. However, when a TFT is manufactured by using aluminum as a wiring material, operation error or deterioration of TFT characteristics were caused by formation of projections such as hillocks or whiskers or by dissemination of aluminum atoms into the channel forming region, in the heat treatment.